On Fri, May 17, 2024 at 03:44:27PM +0800, Chao Gao <chao.gao@xxxxxxxxx> wrote: > On Tue, May 14, 2024 at 05:59:39PM -0700, Rick Edgecombe wrote: > >From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx> > > > >Export a function to walk down the TDP without modifying it. > > > >Future changes will support pre-populating TDX private memory. In order to > >implement this KVM will need to check if a given GFN is already > >pre-populated in the mirrored EPT, and verify the populated private memory > >PFN matches the current one.[1] > > > >There is already a TDP MMU walker, kvm_tdp_mmu_get_walk() for use within > >the KVM MMU that almost does what is required. However, to make sense of > >the results, MMU internal PTE helpers are needed. Refactor the code to > >provide a helper that can be used outside of the KVM MMU code. > > > >Refactoring the KVM page fault handler to support this lookup usage was > >also considered, but it was an awkward fit. > > > >Link: https://lore.kernel.org/kvm/ZfBkle1eZFfjPI8l@xxxxxxxxxx/ [1] > >Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx> > >Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx> > >--- > >This helper will be used in the future change that implements > >KVM_TDX_INIT_MEM_REGION. Please refer to the following commit for the > >usage: > >https://github.com/intel/tdx/commit/2832c6d87a4e6a46828b193173550e80b31240d4 > > > >TDX MMU Part 1: > > - New patch > >--- > > arch/x86/kvm/mmu.h | 3 +++ > > arch/x86/kvm/mmu/tdp_mmu.c | 37 +++++++++++++++++++++++++++++++++---- > > 2 files changed, 36 insertions(+), 4 deletions(-) > > > >diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h > >index dc80e72e4848..3c7a88400cbb 100644 > >--- a/arch/x86/kvm/mmu.h > >+++ b/arch/x86/kvm/mmu.h > >@@ -275,6 +275,9 @@ extern bool tdp_mmu_enabled; > > #define tdp_mmu_enabled false > > #endif > > > >+int kvm_tdp_mmu_get_walk_private_pfn(struct kvm_vcpu *vcpu, u64 gpa, > >+ kvm_pfn_t *pfn); > >+ > > static inline bool kvm_memslots_have_rmaps(struct kvm *kvm) > > { > > return !tdp_mmu_enabled || kvm_shadow_root_allocated(kvm); > >diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c > >index 1259dd63defc..1086e3b2aa5c 100644 > >--- a/arch/x86/kvm/mmu/tdp_mmu.c > >+++ b/arch/x86/kvm/mmu/tdp_mmu.c > >@@ -1772,16 +1772,14 @@ bool kvm_tdp_mmu_write_protect_gfn(struct kvm *kvm, > > * > > * Must be called between kvm_tdp_mmu_walk_lockless_{begin,end}. > > */ > >-int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, > >- int *root_level) > >+static int __kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, > >+ bool is_private) > > is_private isn't used. > > > { > > struct tdp_iter iter; > > struct kvm_mmu *mmu = vcpu->arch.mmu; > > gfn_t gfn = addr >> PAGE_SHIFT; > > int leaf = -1; > > > >- *root_level = vcpu->arch.mmu->root_role.level; > >- > > tdp_mmu_for_each_pte(iter, mmu, gfn, gfn + 1) { > > leaf = iter.level; > > sptes[leaf] = iter.old_spte; > >@@ -1790,6 +1788,37 @@ int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, > > return leaf; > > } > > > >+int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, > >+ int *root_level) > >+{ > >+ *root_level = vcpu->arch.mmu->root_role.level; > >+ > >+ return __kvm_tdp_mmu_get_walk(vcpu, addr, sptes, false); > >+} > >+ > >+int kvm_tdp_mmu_get_walk_private_pfn(struct kvm_vcpu *vcpu, u64 gpa, > >+ kvm_pfn_t *pfn) > > private_pfn probably is a misnomer. shared/private is an attribute of > GPA rather than pfn. Since the function is to get pfn from gpa, how about > kvm_tdp_mmu_gpa_to_pfn()? > > And the function is limited to handle private gpa only. It is an artificial > limitation we can get rid of easily. e.g., by making the function take > "is_private" boolean and relay it to __kvm_tdp_mmu_get_walk(). I know TDX > just calls the function to convert private gpa but having a generic API > can accommodate future use cases (e.g., get hpa from shared gpa) w/o the > need of refactoring. Agreed. Based on a patch at [1], we can have something like int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 gpa, enum kvm_tdp_mmu_root_types root_type, kvm_pfn_t *pfn); [1] https://lore.kernel.org/kvm/55c24448fdf42d383d45601ff6c0b07f44f61787.camel@xxxxxxxxx/ -- Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
